Glass composition and fibers

ABSTRACT

In the technique for fiberizing glass by the use of a centrifugal spinner delivering glass streams into an attenuating blast, a novel spinner construction is provided, and provision is also made for increasing the production, while also providing for the use of glass of lower cost, and at the same time, reducing environmental pollution. Glass compositions and spinner alloy compositions particularly suited for use in accordance with the invention, are also disclosed.

TABLE OF CONTENTS

In connection with the following listing of the headings and inconnection with the text of the specification, it is to be understoodthat not all of the text following each heading is necessarily concernedonly with the subject of the heading, because in numerous places theinterrelationship of different features is explained.

TABLE OF CONTENTS

BACKGROUND

STATEMENT OF THE INVENTION AND OBJECTS

BRIEF DESCRIPTION OF THE DRAWINGS

DETAILED DESCRIPTION OF FIGS. 1 and 1a

OPERATING CONDITIONS AND PARAMETERS

FIGS. 10 AND 11

ADDITIONAL STATEMENT OF PARAMETERS

DETAILED DESCRIPTION OF FIGS. 2 TO 9 INCLUSIVE

GLASS COMPOSITIONS

SPINNER ALLOY

ABSTRACT

BACKGROUND

The present application is concerned with improvements in the techniquefor fiberizing glass or similar thermoplastic materials, especiallymineral materials, in which a centrifugal spinner is employed, usuallymounted on an upright axis, a stream of glass being fed into theinterior of the spinner and being delivered to the inside surface of aperipheral wall of the spinner in which a multiplicity of orifices areprovided, so that upon rotation of the spinner, the glass is projectedby centrifugal force in streams or "primaries" from the orifices in theperipheral wall of the spinner. Provision is made for delivering anannular stream of attenuating gas in the form of a blast from acombustion chamber, the annular stream being directed downwardlyadjacent to the outside surface of the perforate peripheral wall of thespinner, whereby the streams of glass are attenuated and usually alsocoated with a binder and are then carried downwardly in the attenuatingblast to the upper surface of a foraminous collecting conveyor, usuallyarranged as the bottom wall of a collecting chamber. In a typicalinstallation, suction boxes are disposed below the foraminous collectingconveyor in order to assist in the production of a mat or blanket of thefibers on the conveyor, which blanket is carried away for furthertreatment, packaging, etc.

In commonly employed systems of this known type, it has been customaryto employ so-called "soft" glasses, i.e., glass compositions which arespecially formulated to have temperature/viscosity characteristicsproviding a viscosity which will pass freely through the orifices in thespinner wall at a temperature well within the limits of the temperaturewhich the material of the spinner is capable of withstanding withoutexcessive corrosion and deformation.

For the above purpose, the glass compositions employed have customarilyincorporated appreciable quantities of one or more barium, boron, andfluorine compounds, which tend to lower the melting temperature,devitrification of liquidus temperature and the viscosity, and whichhave therefore been effective in avoiding the necessity for employmentof molten glass at excessively high temperatures.

However, the use of compositions containing substantial amounts of boronor fluorine or even barium requires that certain precautions be taken,especially in the case of boron and fluorine because objectionablevolatile constituents may be developed and carried through and out ofthe molten glass production system and, in this event, if thispossibility of pollution is to be avoided, special treatment of thedischarged gases would be necessary in order to separate andappropriately dispose of those constituents.

Barium, boron and fluorine compounds have heretofore been present in theglasses used, typically in amounts respectively about 3%, 6% and 1.5%,but boron and fluorine compounds commonly employed are volatile at thefusion temperature employed in the glass manufacture and fluorine iseven volatile at the temperature employed in fiberization; so that toprovide this content of those ingredients requires initial use of largeramounts in the preparation of the glass, because of the losses due tovolatilization at glass fusion temperatures.

Still another objection to the employment of substantial quantities ofthese compounds is the fact that they tend to increase the cost of thefibers being produced. This latter objection is especially so of bariumcompounds, which are particularly expensive. In addition, the relatively"soft" glasses result in production of glass fibers which are not ashighly temperature-resistant as is desirable.

Various factors heretofore encountered in this type of fiberizationtechnique have also tended to limit the production capacity of a givenplant facility.

STATEMENT OF THE INVENTION AND OBJECTS

Having in mind the foregoing, it is a general objective of the presentinvention to overcome the problems and disadvantages of the priortechniques above referred to.

Thus, the invention contemplates increasing the production of a givenplant facility of the kind employing a centrifugal spinner deliveringstreams of glass into an annular attenuation blast surrounding thespinner; while at the same time, substantially eliminating certainsources of pollution, making possible the use of glass compositions oflower cost, and providing a fiber product having improvedtemperature-resistant characteristics.

With fibers made by a perforated spinner from prior art compositions,insulation products can only be used in applications in which they areexposed to temperatures not substantially in excess of about 400° C.;whereas, with fibers produced from certain compositions according to theinvention, the corresponding temperature may rise to about 480° C.

Various of the foregoing general objectives are achieved by employmentof a number of important improvements herein disclosed individually orin various combinations, including the operating conditions, the methodand equipment employed for feed and distribution of the glass in thespinner, the construction of the spinner itself and also the compositionof the glass, as well as the composition of the alloy from which thespinner is formed. Various of these features are interrelated as will beexplained hereinafter.

It is here further noted that the techniques herein disclosed are alsodisclosed in certain other concurrently filed and related U.S.applications, all of which claim convention priority from FrenchApplication No. 78.34616 filed Dec. 8, 1978.

Turning first to the composition of the glass (examples being givenhereinafter), while the method and the equipment including the spinnerconstruction may be used with presently used compositions, it iscontemplated in the preferred practice of the invention that the glasscomposition be formulated to contain no fluorine and little if anybarium and boron. Such glass compositions are "hard" glasses, havinghigher melting and devitrification temperatures. Indeed, thecharacteristics of fluorine-free compositions and even boron-free aswell as barium-free compositions, although impractical for fiberizationby prior spinner techniques, may readily be fiberized by the method andequipment herein disclosed. Moreover, these hard glasses also result inproduction of "hard" glass fibers which is desirable from the standpointof enhanced temperature performance.

Such hard glass compositions, having elevated devitrificationtemperatures and achieving suitable fiberizing viscosity only at highertemperatures, require special handling and special fiberizing equipment,and the technique disclosed contemplates a number of significantimprovements in the spinner construction, in the method and means fordelivering and distributing the glass in the spinner, and in theoperating conditions established in the spinner, facilitating makingfibers from these hard glasses and even providing for fiberization ofcertain very hard glass compositions which would be difficult, if notimpossible to fiberize with known spinner construction and techniques.

It is here also noted that certain of these structural and operationalimprovements, while of special importance and advantage in thefiberization of hard glasses are also of advantage when used with otherkinds of glass which may be fiberized by the "centrifugal" techniqueunder consideration.

These structural and operational improvements can best be explainedafter consideration of equipment preferably used in the techniquesherein disclosed, and reference is therefore now made to the drawingsand to the following description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertcial sectional view, with some parts in elevation,showing a fiberization production unit incorporating a spinnerconstructed according to one preferred embodiment of the noval hereindisclosed, and having a blast generator for delivering an annularattenuating blast downwardly adjacent to the peripheral wall of thespinner;

FIG. 1a is an enlarged fragmentary view of an alternative feature whichmay be incorporated in the embodiment of FIG. 1;

FIGS. 2, 3, 4, 5 and 6 are partial views similar to FIG. 1, eachillustrating another embodiment of the spinner and the glass feedmechanism within the spinner;

FIG. 7 is an enlarged fragmentary sectional view illustrating anarrangement for mounting a glass feeding device within a spinner; suchas shown in FIG. 6;

FIG. 8 is an enlarged fragmentary sectional view illustrating anarrangement for mounting another form of glass feeding device such asshown in FIGS. 4 and 5;

FIG. 9 is a fragmentary perspective view of spinner bracing structurefor spinners such as shown in FIGS. 4 and 5; and

FIGS. 10 and 11 are fragmentary sectional views through alternativeforms of the peripheral wall of the spinner.

DETAILED DESCRIPTION OF FIGS. 1 AND 1a

Referring first to the embodiment of FIG. 1, a vertical spinnersupporting shaft is indicated at 10, this shaft carrying at its lowerend a hub for mounting the spinner, the hub being indicated at 11. Thespinner itself is indicated in general at 12. The spinner is made up ofa peripheral wall 13 having a multiplicity of rows of spinner orifices,and the upper edge of the wall 13 is connected to the hub 11 by thecentral mounting portion or neck 14. The orifices in the spinner wallare illustrated only in the sectioned portions of the spinner wall butit is to be understood that a multiplicity of orifices are provided ineach of a plurality of vertically spaced rows of orifices. At its loweredge, the spinner is provided with an inwardly projecting flange 15 towhich the upper edge of a cylindrical part or element 16 is connected,this cylindrical part serving a reinforcing or bracing function, as willfurther be explained.

Mounted within and rotating with the spinner is a distributing basket 17having a single series of distributing orifices 18 which are locatedsubstantially in the plane of the uppermost row of orifices in theperipheral wall of the spinner. As shown, the basket 17 is mounted onthe hub 11 by means of depending brackets 17a. A stream of glass isdelivered downwardly and centrally through the spinner mountingstructure, as is indicated at S, being delivered to the inside of thebottom wall of the basket 17, and spreading laterally on that bottomwall to the perforate peripheral wall of the basket, so that the glassbuilds up a layer on the inside of the basket wall, from which streamsindicated at 19 are projected through the orifices radially outwardly tothe inside surface of the peripheral wall of the spinner adjacent to theuppermost row of orifices from which zone the glass flows downwardly onthe inside surface of the spinner wall. This downward flow isunobstructed, there being no interior confining wall or chamberstructure inside of the peripheral wall, and the flow has laminarcharacteristics, when viewed under stroboscopic light, in which there isthe appearance of smooth waves. It is from this unobstructed orunconfined laminar flow layer that the glass enters the orifices in theperipheral wall of the spinner and is projected therefrom outwardly fromall of the spinner orifices, in a multiplicity of streams or primarieswhich are subjected to attenuation by the annular gas blast which isestablished by equipment described hereinafter.

FIG. 1a shows an alternative distributor basket 17b having two rows oforifices 18a arranged in staggered fashion but all positioned close to acommon plane for delivering the glass to the region of the uppermost rowof orifices in the spinner wall.

In connection with the arrangement of the distributor basket (17 in FIG.1 and 17b in FIG. 1a), it is pointed out that most of the distributorbaskets employed in prior art techniques are provided with several rowsof orifices vertically spaced from each other in order to provide fordistribution of the glass to the perforated peripheral wall of thespinner throughout much of the vertical dimension of the perforatespinner wall. We have found, however, that in providing the multiplicityof orifices required to effect the vertical distribution of the glass inaccordance with the common technique of the prior art, certaindisadvantages and difficulties were encountered, especially inconnection with spinners of relatively large size, both with respect todiameter and vertical height of the perforate peripheral wall.

One of the most important problems relates to heat loss from the streamsof glass being delivered from the distributor basket to the inside ofthe peripheral wall of the spinner. Such heat loss is directlyproportional to the total surface area of the delivered streams. With alarge number of small streams, as in prior arrangements, the totalsurface area is much greater than with the arrangement herein disclosedin which the distributor basket is provided with only one row oforifices of larger size, thereby effecting delivery of the same quantityof glass with much smaller total surface area. Indeed, in a typicalcase, the arrangement as herein disclosed provides for delivery of agiven quantity of glass in streams having only about 1/7 of the surfacearea of prior arrangements.

The improved arrangement therefore eliminates the excessive heat lossfrom the glass being delivered from the distributor basket to theperipheral spinner wall, which was a major disadvantage of the prior artequipment. Moreover, with the smaller streams of glass used in priortechniques, the temperature loss in delivery from the distributor basketto the peripheral wall of the spinner is much less uniform as betweendifferent streams, than is the case where a smaller number of largerstreams are provided, as in the arrangement of the present invention.

Although the foregoing problems of heat loss were not considered to beprohibitive when using the softer glasses employed in the prior arttechniques, when using the harder glasses herein contemplated, such heatlosses can not be tolerated.

Another factor of importance is that the technique herein disclosedcontemplates increasing the diameter of the spinner. With glass streamsof small diameter delivered from the distributor basket, as in priorarrangements, the increase in the spinner diameter tends to result influttering of the streams thereby adversely influencing uniformity ofoperating conditions. The use of a smaller number of larger streamsovercomes such fluttering. Other means for reducing such flutteringtendencies are described hereinafter with reference to embodiments shownin FIGS. 2 to 6.

Still further, with many smaller streams of glass delivered to theinside of the perforate peripheral spinner wall throughout most of theperforate area of that wall some of the streams arrive at the perforatedwall in substantial alignment with individual perforations in the wall,whereas others arrive at the perforated wall in imperforate areasbetween the perforations of the spinner wall; and this has introducednon-uniform dynamic conditions tending to adversely affect theuniformity of the fibers being produced.

With the foregoing in mind, instead of employing a multiplicity ofsupply streams distributed vertically over the peripheral spinner wall,the improved arrangement provides for establishing and maintaining anunrestrained, unconfined and downwardly flowing layer of molten glass onthe inside surface of the perforated peripheral wall, the feed of theglass being effected to the upper edge of that layer and the layerflowing downwardly in laminar fashion over all of the perforations ofthe spinner wall, so that the dynamic conditions for projecting thestream of glass through and from each perforation of the peripheral wallare substantially the same, thereby eliminating a source ofnon-uniformity of the fibers produced.

This development or establishment of the downwardly flowing unconfinedlayer is effected by the distributor basket arrangement described abovein connection with FIGS. 1 and 1a, i.e., by the employment of a basketor distribution system in which all of the glass to be fiberized isdelivered to the spinner wall through a single series of orifices closeto or in a plane located at or close to the level of the uppermost rowof perforations in the spinner wall. This single series of orificesdesirably comprises a total of only about 75 to 200 orifices, which isabout 1/10 to about 1/3 of the number commonly used in multiple rowdistributor baskets.

The establishment of the desired uniform conditions for feed of theglass through the perforations in the spinner wall is further enhancedby certain other preferred operating conditions described hereinafter,particularly the maintenance of temperature conditions which willestablish substantially uniform viscosity of the glass in the upper andlower regions of the spinner wall.

For the purpose of the attenuation, the structure, as shown in FIG. 1,includes an annular chamber 20 with an annular delivery orifice 21, thechamber 20 being fed from one or more combustion chambers such asindicated at 22 supplied with appropriate means for burning fuel andthus producing the desired hot attenuating gases. This provides adownwardly directed annular stream of attenuating gas in the form of acurtain surrounding the spinner. The details of construction of thespinner mounting structure and of the blast generator need not beconsidered herein as they are well known in this art.

As seen in FIG. 1, the equipment also includes a means for heating thelower edge of the spinner. This may take a variety of forms andpreferably comprises a high frequency heating device in annular form, asindicated at 23. The heater ring is desirably larger in diameter thanthe spinner and is preferably spaced slightly below the bottom of thespinner.

OPERATING CONDITIONS AND PARAMETERS

Turning now to the operation of an embodiment such as illustrated inFIG. 1, it is first pointed out that while various features hereindisclosed may be used with spinners of any size, it is contemplatedaccording to the preferred practice of the improved technique that thespinner be of larger diameter than has been customary heretofore. Forexample, the spinner may be of the order of 400 mm in diameter, ascompared with 300 mm which has been typical with many spinnersheretofore employed. This makes possible the employment of asubstantially increased number of glass delivery orifices in theperiphery wall of the spinner, which is of advantage in order toincrease the number of streams of glass projected from the spinner intothe surrounding blast for attenuation. Because of the relatively highrates of rotation of spinners of this type, the spinner wall issubjected to a very substantial centrifugal force; and since the spinneroperates at elevated temperature, there is always a tendency for the midregion of the peripheral wall to bow outwardly. This tendency isresisted by the use of reinforcement or bracing means, several forms ofwhich are disclosed in the various embodiments shown in the drawings. Inthe embodiment of FIG. 1, the reinforcing means takes the form of anangular element 16 mounted by means of the inturned flange 15 at thelower edge of the peripheral wall. The reinforcing action of thisannular element 16 will be understood if it is kept in mind that thetendency for the central region of the peripheral wall 13 to bowoutwardly under the action of centrifugal force tends to flex the flange15 upwardly and inwardly about the line of junction of the flange withthe lower edge of the wall 13. If the annular element 16 were notpresent (as is the case in prior spinners) a limited amount of thisupward and inward flexing of the flange 15 is accommodated by theformation of slight "waves" or ripples in the relatively thin inner edgeof the flange 15. However, with the annular element 16 joined to theinner edge of the flange such rippling of the inner edge of the flangeis inhibited, thereby providing reinforcement or bracing of the wallstructure of the spinner. The angular junction of the element 16 withthe flange 15 also aids in providing the desired reinforcement.

For the purpose just described, the bracing element 16 preferably has adimension axially of the spinner greater than the average wall thicknessof the peripheral spinner wall 13 and desirably even greater than themaximum thickness of the spinner wall. Moreover, in order to provide thedesired action for resisting the outward bowing of the peripheral wall,the annular element is desirably mounted in position projectingdownwardly from the inner edge of the flange 15. It has been found thatreinforcement of the spinner in the manner disclosed herein results inretarding the bowing of the spinner wall, with consequent increase inthe useful life of the spinner.

Other configurations of structures for accomplishing this reinforcingaction are disclosed in other figures described hereinafter.

Before considering a preferred operation of an embodiment of theequipment such as shown in FIG. 1, it is first pointed out that in atypical prior art operation employing a spinner with a relatively softglass, the glass is customarily delivered into a distributor basketmounted in the central region of the spinner and having a peripheralwall with a plurality of vertically spaced rows of glass distributingorifices so that the glass is delivered from the basket throughout atleast most of the vertical dimension of the peripheral wall of thespinner. In such a prior typical operation, a substantial temperaturedifferential exists as between the upper edge portion of the peripheralwall and the lower edge portion of the peripheral wall. Thus, the upperedge portion is at higher temperatures than the lower edge portion,primarily because of the proximity of the upper edge portion to theorigin of the attenuating blast. Moreover, in a typical case, theperipheral wall is of the same thickness throughout its height, or insome cases is thicker toward the top edge than toward the bottom edge.In addition, in this prior typical technique, there may be somedifferential in the size (diameter) of the orifices in the upper rows ofthe spinner as compared with the lower rows thereof. These variousfactors have heretofore been established in order to provide forprojection of the glass streams to a greater extent from the upperorifices than from the lower orifices, in order to obtain what has beenreferred to as "umbrella" fiberization, as disclosed, for example, inFIG. 3 of the Charpentier et al U.S. Pat. No. 3,304,164. This avoidshaving the fibers cross each other and become entangled or fused to eachother in the fiberizing zone, as is the case if the glass streams areprojected to the same extent from both the lower and upper rows oforifices.

Although the lower edge of the spinner in certain of these prior arttechniques has been subjected to some heating in addition to thatresulting from the surrounding attenuating blast and the introduction ofthe molten glass, the achievement of umbrella fiberization in thetypical prior art techniques has most commonly required operation at adifferential in the glass temperature as between the upper edge of thespinner and the lower edge of the spinner. The upper edge of the spinnerwas at a higher temperature because of factors already referred to, andthe lower edge of the spinner was commonly at lower temperature, evenwhere some heat was added; and because of this differential intemperature, for instance from about 1050° C. toward the top to 950° C.toward the bottom, the resultant viscosity of the glass was lower at thetop than at the bottom, with consequent greater flow or pull ratethrough the upper holes, and the streams of glass were thereforeprojected farther at the top than at the bottom of the spinner, and thisachieved the desired umbrella fiberization.

With the prior art techniques employing soft glasses, such a temperaturedifferential between the upper edge and the lower edge of the spinnercould be resorted to for the purposes referred to because with the softglass even when the temperature was elevated substantially above thedevitrification temperature (and the glass employed at that elevatedtemperature adjacent the upper rows of orifices), the temperature wasstill not so high as to result in serious adverse effect upon the metalof the spinner.

In contrast with the foregoing, with a hard glass, it is not practicalto operate with a substantial temperature differential between the upperand lower edge portions of the spinner. The reason for this is that ifthe temperature at the lower edge portion is established at a levelsufficiently above the devitrification temperature to avoidcrystallization of any of the glass, with consequent clogging of thelower rows of orifices, then in order to establish the temperaturedifferential frequently used in the prior art techniques to accomplishthe umbrella fiberization, it would be necessary to elevate the glasstemperature adjacent the upper edge of the spinner to such a high valuethat the spinner is subjected to prohibitive corrosion, erosion and/ordistortion.

Taking these factors into account, the improved technique provides forthe accomplishment of the desired umbrella fiberization in a novelmanner when employing hard glass compositions. Instead of utilizing atemperature differential between the upper and lower edges of thespinner, the improved technique establishes approximately the sametemperature at the upper and lower edges of the spinner, and thistemperature is established at a level (for instance 1050° C.) which isabove and yet relatively close to the devitrification temperature. Theviscosity of the glass will therefore be essentially the same toward thetop and bottom rows of orifices of the spinner, for example about 5000poises; and the desired increased resistance to projection of the glassstreams from the lower rows of orifices is achieved in accordance withthe improved technique in a different manner. Thus, in contrast with theprior art, the improved technique contemplates utilizing a peripheralspinner wall which is of greater thickness toward the bottom edge thantoward the top edge, as is clearly shown in FIG. 1. This results inorifices toward the bottom edge which are of greater length and which,with a given viscosity of the glass, offer a greater resistance toprojection of the glass streams under the action of centrifugal force.With such greater resistance to projection of the streams, the streamswill be projected to a greater extent at the upper edge of the spinneras compared with the lower edge, thereby producing the desired umbrellafiberization. If desired, the resistance to projection of the glassstreams through the orifices in the lower rows may be further increasedby utilizing orifices of smaller diameter in the lower rows.

For establishing the desired temperature at the lower edge portion ofthe spinner, it is contemplated to provide more intense heating of thelower edge of the spinner than has heretofore been utilized. Thus, theheater 23 in FIG. 1 should have at least two to three times the power ofheaters heretofore used. A heater of 60 kw capacity at 10,000 Hz issuitable.

In the preferred practice herein disclosed, it is contemplated thatconditions be maintained establishing a temperature of the glass in theregion of both the top and bottom portions of the peripheral spinnerwall at a level from about 10° C. to about 20° C. above thedevitrification temperature of the glass being used.

For most purposes, it is also contemplated that the lower edge portionof the peripheral wall of the spinner should be at least about 11/2times the thickness of the upper edge portion of the peripheral wall ofthe spinner; and in some cases, it may be desirable to proportion thespinner wall so that the lower edge portion is as much as 21/2 times thethickness of the upper edge portion. A spinner having a lower edgeportion approximately twice the thickness of the upper edge portion istypical in the practice of the present invention. For example, in such atypical spinner, the upper edge portion of the spinner may be 3 mm inthickness and the lower edge 6 mm in thickness.

FIGS. 10 AND 11

At this point, attention is further directed to FIG. 10 whichillustrates on an enlarged scale the cross section of a peripheralspinner wall having a greater thickness toward the bottom than towardthe top. Although the increase in thickness from top to bottom may besubstantially uniform, as is illustrated in FIG. 1, the alternative asshown in FIG. 10 may also be employed. In this alternative, it will benoted that the thickest part of the wall is toward the bottom edge andthe thinnest part in the mid region, while the upper edge portion is ofintermediate thickness. This type of graduation of wall thickness may beemployed to advantage to even more accurately establish the desiredumbrella fiberization. In this connection, it should be kept in mindthat the two principal sources of heating the peripheral wall are theattenuating blast toward the top, and the induction heater 23 toward thebottom. In consequence of this, the mid region of the peripheral wallwill assume a temperature somewhat lower than either the top or thebottom edges, and the viscosity of the glass in the mid region wouldtherefore be correspondingly higher. The change in wall thickness, asshown in FIG. 10, would therefore assist in establishing the extent offlow and projection of the glass desired, i.e., maximum flow andprojection at the top, intermediate flow and projection in the midregion and minimum flow and projection at the bottom.

Although in FIG. 1 and in FIG. 10, the outer surface of the wall isshown as being conical, i.e., of slightly larger diameter toward thebottom than toward the top, the outer surface may be cylindrical, as isshown in FIG. 11.

ADDITIONAL STATEMENT OF PARAMETERS

Before proceeding with description of alternative embodiments and otherrelated features, such as are illustrated in FIGS. 2 and 9 inclusive, itis desired to point out certain additional parameters, including rangesof both structural and operational features of the invention.

Although various features of the invention may be utilized inassociation with spinners having a coefficient of perforation (i.e., theratio of the entire perforation area to total area) of the peripheralwall of the order of magnitude employed in the prior art, some featuresherein contemplated are advantageously used in association with aspinner having an increased number of holes per unit of surface area ofthe peripheral wall. By such increase in the coefficient of perforation,it is possible to increase the pull rate of the spinner, i.e., the totalquantity of glass fiberized by the spinner.

In analyzing this manner, it must be kept in mind that the rate ofdelivery of glass through the perforations of the spinner wall isgreatly influenced by the viscosity of the glass being delivered.Increase in viscosity will retard the flow through each individualperforation; but with an increased coefficient of perforation, a givenoverall pull rate for a spinner may be maintained even with glass ofhigher viscosity. Increase of the perforation coefficient, therefore,provides for utilization of glasses at a higher viscosity thancustomarily employed with spinners, without resulting in decrease of theoverall pull rate of the spinner.

As the pull rate is also dependent upon the diameter of the individualperforations, a given pull rate per spinner may be maintained even withindividual perforations of decreased diameter, provided that theperforation coefficient is sufficiently increased.

Although the disclosed technique contemplates increase in the overallproduction or pull rate of a given spinner, it is also contemplated thatthis be accomplished while at the same time reducing the rate of passageof the glass through the individual perforations in the spinner wall.This result may be achieved in part by increasing the coefficient ofperforation (as already pointed out above) and also by certain otherfactors mentioned hereinafter; and in consequence, erosion anddeterioration of the spinner is reduced, notwithstanding the increase inoverall pull rate. The erosion is, of course, concentrated in theindividual perforations and it is unexpected that despite the increaseof the perforation coefficient (which would be expected to weaken thespinner), the output and life of the spinner is not reduced; but mayeven be somewhat extended compared with prior techniques.

Moreover, with a decreased rate of flow of the glass through theindividual perforations, the velocity of the attentuating blastdelivered adjacent the outside surface of the peripheral spinner wallneed not be as high as in case of a higher rate of flow through theindividual perforations. This has a two-fold advantage.

First, it provides for the production of fibers of greater length,because as is known, the length of the fibers produced by a spinner ofthe type here under consideration is, in general, inversely proportionalto the speed of the attenuation gases. Second, the decrease in the speedof the attenuation gases effects an energy saving.

Increase in the perforation coefficient also provides for attenuation ofa larger number of filaments in a given volume of the attenuation gasesand this represents a further capability for energy conservation. It hasbeen found that in the technique herein disclosed, notwithstanding theincrease in the number of filaments per unit of volume of theattenuating gases, the fibers produced do not have pockets or areas ofconglomerated fibers, but the fibers remain individually isolated fromeach other during their entire attenuation, thereby producing fibrousproducts such as insulation of high quality.

It is herein contemplated that for most purposes the coefficient ofperforation should be such as to provide at least 15 perforations persquare centimeter of the perforated part of the peripheral wall; forinstance, between 15 perforations and 45 or 50 perforations per squarecentimeter. A preferred value is about 35 perforations per squarecentimeter. The diameter of the perforations used is preferably fromabout 0.8 mm to about 1.2 mm.

Although certain features may be used with spinners of any diameter, formany purposes, it is contemplated to increase in the diameter of thespinner, as compared with spinners used in the prior art. Thus, whereasa typical spinner according to the prior art has a diameter of about 300mm, it is herein contemplated that the spinner may have a diameter of atleast 400 mm and as high as 500 mm.

Increase in the diameter of the spinner also presents certainadvantages. Thus, for a given perforation coefficient and the same pullrate of glass through the spinner, an increase in diameter provides fora decrease of the rate of flow of glass through the individual orifices.As pointed out above in connection with the increase in the coefficientof perforation, the decrease in rate of flow through the individualperforations may even permit some increase in the viscosity of the glassbeing delivered. Even at the same overall pull rate for the spinner,glass at the higher viscosity will not produce excessive wear because ofthe lower flow rate through the individual orifices.

Although certain features may be employed with spinners in which theperipheral wall is of any desired vertical dimension, it is alsocontemplated that for some purposes the peripheral wall of the spinnermay be of increased height, even twice as high as prior spinners, forinstance, the height of the spinner may be increased from about 40 mm toabout 80 mm. Such increase in height may be resorted to for increasingthe total number of perforations provided, and increase in the totalnumber of perforations provided in this way is advantageous because anincreased number of glass streams or primaries are projected into theattenuation current, thereby effecting a further energy conservation.

DETAILED DESCRIPTION OF FIGS. 2 TO 9 INCLUSIVE

Turning now to the embodiment illustrated in FIG. 2, it is noted that acentral spinner mounting shaft 10 is again provided, at the lower end ofwhich the hub structure 24 is mounted, providing for support of thespinner generally indicated at 25. As in the first embodiment, anannular chamber 20 having an annular blast delivery orifice 21 isprovided, in order to deliver the attenuating blast adjacent to theperipheral wall of the spinner. In FIG. 2, the diameter of the spinneris somewhat greater than in FIG. 1, and the peripheral spinner wall 26is again of greater thickness toward the lower edge than toward theupper edge thereof. At the lower edge of the peripheral wall, aninturned flange 27 is provided, this flange being of progressivelyincreasing thickness radially inwardly, with the inner edge having adimension axially of the spinner at least as great as the averagethickness of the wall 26 and preferably greater than the maximumthickness of the wall 26. Bracing is thereby provided to resist outwardbowing of the peripheral wall 26 in the central region thereof in themanner disclosed above.

In the embodiment of FIG. 2, a distributor basket 28 is mounted in thecenter of the spinner, being provided with a series of peripheralorifices 29. The glass stream S enters the basket from above, as in FIG.1, and the rotation of the delivery basket 28 provides for radiallyoutward discharge of streams 30 of the glass.

Instead of direct delivery of the streams 30 to the inside of theperipheral wall of the spinner, the embodiment of FIG. 2 includes arelay device interposed between the supply basket and the peripheralwall of the spinner. This relay device takes the form of an annularinwardly open funnel 31 having a series of spaced relay orifices in thebottom of the funnel for delivery of streams of glass indicated at 32 tothe peripheral wall of the spinner. As in the embodiment firstdescribed, it is contemplated that the orifices delivering the streams32 should be located so as to deliver all of the glass to be fiberizedin the region of the upper portion of the perforate wall of the spinner,thereby providing for the unobstructed laminar flow downwardly asalready described.

In the embodiment of FIG. 2, it will be noted that the diameter of thesupply basket 28 is smaller than the diameter of the basket 17 in FIG.1, notwithstanding the fact that the spinner diameter of FIG. 2 islarger than the spinner diameter in FIG. 1. This proportioning of theparts in question is desirable, because, even with a delivery basket ofdiameter such as that of the basket 17 shown in FIG. 1, the distance ofthe perforated spinner wall from the distributor basket would impair theuniformity of the delivered streams and cause fluttering of the streams,with consequent delivery of some of the glass to a region of the spinnerwall below the upper edge portion. This is undesirable because it isherein contemplated that all of the glass be delivered substantially inthe plane of the uppermost rows of orifices in the spinner wall, so asto provide the desired unobstructed laminar or layered downward flowfrom the top to the bottom of the peripheral spinner wall.

By employing a distributor basket 28 of somewhat smaller diameter thanthat shown in FIG. 1, and further employing a relay device such as theannular funnel 31 shown in FIG. 2, the glass delivery can be moreaccurately effected to the region of the uppermost row of spinnerorifices. The funnel 31 may be mounted on a portion of the hub structure24 by a bracket supporting structure such as indicated in outline at31a. This mounting preferably includes insulating means (for example, asshown at 46 in FIGS. 7 and 8).

As in FIG. 1, a high frequency induction heating device 23 may also beemployed in FIG. 2 in order to provide the desired equalization oftemperature of the upper and lower edge portions of the perforate wallof the spinner.

FIG. 3 illustrates an embodiment similar to FIG. 2 and correspondingreference numerals have been applied to parts of the same or closelysimilar construction. The spinner 25 and also the distributor basket 28are, in fact, of identical construction as compared with FIG. 2; but inthe embodiment of FIG. 3, instead of employing the annular inwardly openfunnel 31, the embodiment of FIG. 3 employs a relay device 33 ofdifferent construction. This device 33 comprises an annular ring mountedon the hub structure by means of bracket supports 33a (with insulatingmeans, as in FIGS. 7 and 8). The ring has an inwardly open groove forreceiving the streams 30 of glass delivered from the basket 28 and thelower edge of the groove is defined by a dam or overflow ridge 34, sothat the glass received by the relay ring 33 overflows and is deliveredby centrifugal force to the inside of the peripheral wall of thespinner. Preferably, the relay ring 33 is positioned so that theoverflow dam will deliver the glass in the plane of the uppermost row oforifices in the spinner wall.

The functioning of the embodiment of FIG. 3 is similar to that of FIG.2, except that in the case of the funnel 31 of FIG. 2, individualstreams 32 of glass are discharged from orifices at the base of afunnel, whereas in FIG. 3, the glass is delivered by the relay device ina body of sheet-like form, as indicated at 35, rather than in individualstreams.

Turning now to the embodiment of FIG. 4, the spinner 36 there shown isof substantially increased vertical dimension as compared with thespinners in FIGS. 1, 2 and 3. In FIG. 4, a distributor basket 28 similarto that described above in connection with FIG. 3 is employed, and thisbasket delivers streams of glass 30 to the annular relay device 33, ofconstruction similar to that described above in connection with FIG. 3.However, in FIG. 4, the relay device 33 does not deliver the glassdirectly to the inside of the spinner wall; but, instead, delivers theglass into the interior of an annular inwardly open funnel 37 which ismounted on a structure 38 lying within the spinner and connected withthe spinner toward its upper edge.

The structure 38 is of generally cylindrical form with its upper edgesecured to the neck portion of the spinner and having at its lower edgean annular socket 38a for receiving the down turned edge 36a provided onthe inturned flange at the bottom of the spinner. The structure 38 isalso connected with a bottom plate 38b. Both the structure 38 and thebottom plate are preferably provided with spaced apertures, as shown.Peripherally spaced anchors or brackets 39 (see also FIG. 9) extendinwardly from the central portion of the peripheral wall of the spinnerand serve to mount a ring 39a which engages peripherally spaced sockets38c provided on the supporting structure 38. The peripheral spacing ofthe brackets 39 avoids any appreciable restraint or disturbance of thelaminar flow of the glass on the inside surface of the spinner wall. Theinterengagement of the parts 36a-38a, and 39a-38c is arranged to providefreedom for relative vertical expansion and contraction of thesupporting structure 38 and the peripheral wall of the spinner. Thissupporting structure, expecially the parts 39, 39a and 38c, provideeffective bracing for the peripheral wall of the spinner, therebyresisting outward bowing of the spinner wall under the action ofcentrifugal force.

An advantage of this structure is that the supporting members aremaintained at a lower temperature; for example, while the spinnerperipheral wall is typically at a temperature of about 1050° C. duringoperation, the supporting structure can be about 600° C., and thusremain more rigid.

Certain details of the construction of the relay funnel 37 and of themounting structure 38 are illustrated in the enlarged sectional view ofFIG. 8. From this view, it will be seen that individual deliveryapertures 40 in the base of the funnel are positioned to deliver streamsof glass through radially aligned apertures 41 formed in the supportingstructure 38.

The spacing of the brackets 39 at intervals around the inside of thespinner wall makes possible the development of the desired laminar flowof the glass from the upper region of the spinner to the lower regionthereof, with a minimum of interruption.

Other parts of the equipment, for instance, the journal mounting of thespinner, the annular chamber and annular orifice for the attenuationgases, and the heating element 23 may all be similar to those alreadydescribed above.

In the embodiment of FIG. 5, the spinner 42 is of construction similarto that of the spinner 36 in FIG. 4, but the spinner in FIG. 5 is ofsmaller diameter, and for purposes of the glass supply, the arrangementof FIG. 5 includes a central distributor basket 43 of somewhat largerdiameter than that shown at 28 in FIG. 4, and this basket has peripheralapertures delivering streams 44 of glass directly into the relay funnel37, instead of through the intermediation of the overflow relay device33. This embodiment includes supporting structure 38, a centrallycut-out bottom plate 38b, and connections with the peripheral wall ofthe spinner, as described above with reference to FIG. 4.

Although various features of the arrangements of FIGS. 4 and 5 may beused with peripheral walls of uniform thickness, it is preferred thatthe wall thickness be increased toward the bottom edge, for reasonsalready pointed out.

In FIG. 6, a construction is illustrated similar to that of FIG. 3, thespinner 25 being the same as the spinner in FIG. 3. Moreover, thedistributor basket 28 is the same as in FIG. 3; but in FIG. 6, anoverflow relay ring 45 is employed and (see also FIG. 7) the ring inthis embodiment is mounted directly upon a portion of the spinner wallitself, rather than upon the hub structure, as in FIG. 3.

In the detailed views of FIGS. 7 and 8, it will be noted that in bothcases, the mounting of the relay device (37 in FIG. 8 and 45 in FIG. 7)includes an interposed layer of insulating material 46 which is providedin order to diminish heat transfer from the relay device to the spinner,and in the case of the embodiment of FIGS. 4, 5 and 8 in order todiminish heat transfer to the supporting structure 38.

GLASS COMPOSITIONS

One of the highly desirable characteristics of the technique hereindisclosed is that the structural and operational features may beemployed with a wide range of glass compositions.

Thus, various of the structural and operational features above referredto may be employed individually and in combination with many knownattenuable glass compositions, including "soft" glasses. In addition,various of the individual features and combinations may also be usedwith certain types of glass compositions which have not customarily beenemployed in prior fiberizing operations employing a centrifugal spinnerfor the projection of glass primaries into an attenuating blast. Indeed,with the spinner and technique herein disclosed, glass compositions mayreadily be used which are not practical to use in prior spinnerequipment and techniques for various reasons especially because of therelatively high devitrification temperature requiring the use ofrelatively higher spinner temperature. Such higher spinner temperatures,if used with prior art spinners, would result in deterioration (erosionand/or outward bowing of the peripheral wall) so rapidly that thespinner would not have practically or industrial life. Indeed, with someof the glass compositions contemplated for use in the technique of thepresent invention, it would be virtually impossible to effectfiberization with prior art spinners.

Still further, it is contemplated to use certain glass compositions noteven known heretofore, having desirable temperature/viscositycharacteristics particularly suited to use in the improved techniquesdisclosed; and these novel glass compositions are also advantageous inthat they do not incorporate fluorine compounds and may even besubstantially free of one or even both of boron or barium compounds, allthree of which (fluorine, boron, barium) have heretofore commonly beenused individually or in combination in significant quantities in theformulation of glass compositions for fiberization in spinnertechniques. In consequence, these particular glass compositions areespecially advantageous in that they are economical and substantiallyfree of pollution problems. The novel compositions referred to, havingrelatively high melting and devitrification temperatures also result inproduction of fibers having improved temperature-resistantcharacteristics. Thus, heat insulation products prepared from such novelglass compositions may be safely used in application in which theinsulation is subjected to temperatures as high as 450° to 500° C.,which compares with a temperature of about 400° C. for insulationproducts made with fibers formed of various of the known "soft" glasses.

Preferred glass compositions contemplated for the improved techniquesherein disclosed, not only are characterized by various featureshereinabove referred to, but in addition, such preferred glasses,desirably have compositions conforming with the examples and rangesgiven hereinafter. Before specifically identifying such compositions, itshould be remembered that under conventional prior art conditions, theglass viscosity used was of the order of 1000 poises at the operatingtemperature of fiberization. Thus, a devitrification temperature as lowas possible was sought; and such low temperatures could only be attainedby addition of fluorine compounds or even boron and barium compounds. Incontrast, in the improved technique, using the disclosed novel glasscompositions, the glass may have a viscosity of the order of 5000 poisesat the operating temperature of the spinner, and a spinner temperatureof 1030 to 1050° C., i.e., barely above the liquidus, is employed.

In considering the compositions of various glass formulations which maybe used with the equipment and technique herein disclosed, it is againnoted that the improved equipment and technique may be used with a widevariety of glass formulations heretofore known and used; butparticularly desirable results are attained when employing formulationsof certain compositions which have not been known, have not beenemployed heretofore or are not well adapted for use with the prior artspinner techniques. In the Table I just below, 8 different compositionsin these categories are identified, with the exception of minorunidentified impurities, all figures representing parts by weight. Thistable also shows the principal characteristics of these 8 compositions.

                                      TABLE I                                     __________________________________________________________________________    CONSTITUENT  0   1   2   3   4   5   6   7                                    __________________________________________________________________________    SiO.sub.2    66.9                                                                              63.15                                                                             62.6                                                                              62.7                                                                              61.6                                                                              63.45                                                                             62.1                                                                              60.3                                 Al.sub.2 O.sub.3                                                                           3.35                                                                              5.05                                                                              5.2 5.15                                                                              5.9 5.25                                                                              5.85                                                                              6.35                                 Na.sub.2 O   14.7                                                                              13.2                                                                              15.15                                                                             15.2                                                                              13.8                                                                              14.95                                                                             14.55                                                                             14.95                                K.sub.2 O    1   2.1 2.3 2.3 2.45                                                                              2.25                                                                              2.7 2.65                                 CaO          7.95                                                                              5.9 5.25                                                                              5.5 5.95                                                                              5.4 5.75                                                                              6.25                                 MgO          0.3 2.65                                                                              3.35                                                                              3.35                                                                              2.6 4   2.75                                                                              2.4                                  BaO          trace                                                                             2.9 4.85                                                                              2.7 3.2 trace                                                                             trace                                                                             trace                                MnO          0.035                                                                             2   trace                                                                             1.5 3.05                                                                              3   3.4 2.9                                  Fe.sub.2 O.sub.3                                                                           0.49                                                                              0.78                                                                              0.79                                                                              0.85                                                                              0.89                                                                              0.84                                                                              1.88                                                                              3.37                                 SO.sub.3     0.26                                                                              0.55                                                                              0.5 0.52                                                                              0.45                                                                              0.51                                                                              0.4 0.36                                 TiO.sub.2    trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                B.sub.2 O.sub.3                                                                            4.9 1.5 trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                                                             trace                                PROPERTIES                                                                    VISCOSITY                                                                     T(log = 2)                                                                             ° C                                                                        1345                                                                              1416                                                                              1386                                                                              1403                                                                              1410                                                                              1402                                                                              1405                                                                              1395                                 T(log = 2.5)                                                                           ° C                                                                        1204                                                                              1271                                                                              1249                                                                              1264                                                                              1270                                                                              1265                                                                              1266                                                                              1257                                 T(log = 3)                                                                             ° C                                                                        1096                                                                              1161                                                                              1141                                                                              1156                                                                              1158                                                                              1160                                                                              1158                                                                              1150                                 T(log = 3.7)                                                                           ° C                                                                         975                                                                              1042                                                                              1028                                                                              1038                                                                              1042                                                                              1045                                                                              1038                                                                              1030                                 DEVITRIFI-                                                                    CATION                                                                        Liquidus ° C                                                                         970                                                                              1020                                                                               960                                                                              1015                                                                              1015                                                                              1040                                                                              1020                                                                              1025                                 Maximum crys-                                                                 tal growth                                                                             um/mn                                                                             0.93                                                                              0.52                                                                              0.3 0.46                                                                              1.1 0.4 1.08                                                                              1.96                                 At tempera-                                                                   ture of  ° C                                                                        855 900 840 800 900 880 915 920                                  CHEMICAL                                                                      RESISTANCE                                                                    H.sub.2 O attack-                                                             ability  mg  13.6                                                                              10.8                                                                              16.5                                                                              16.8                                                                              11  16.4                                                                              12.86                                                                             14.9                                 Attack   mg                                                                   Resistance                                                                             Na.sub.2 O                                                                        4.6 3.6 5.9 5.9 3.6 5.6 4.8 4.9                                  __________________________________________________________________________

In connection with the percentages of the several ingredients givenabove, while the table presents figures from analysis of actual sampleglasses, it will be understood by those skilled in the art that somerange for each constituent is appropriate, for example, up to about plusor minus five percent while still remaining within the overall rangegiven in Column C of Table II herebelow, because of variations in thechemical composition of batch constituents, variations resulting fromvolatilization in the glass melting furnace, and limitations on theprecision with which the weight values and chemical analysis values canbe measured.

Although composition 0 could be fiberized with certain known spinnertechniques, such fiberization would not be economically feasible from anindustrial point of view, because with known techniques, the productionor pull rate would be unacceptably low. However, with the technique ofthe present invention, composition 0 can be used economically.

The other compositions would be virtually impossible to fiberize on anindustrial basis by known centrifugal spinner techniques; and incontract, these other compositions are particularly well adapted to usein the improved technique herein disclosed. Certain of these otherformulations, such as, for example, compositions 5, 6 and 7 have notbeen known heretofore, and of these, composition 6 is preferred.

The equipment and technique herein disclosed may be employed with quitea broad range of glass compositions, for instance, as indicated incolumn A of Table II herebelow.

                                      TABLE II                                    __________________________________________________________________________                A      B            C                                                                GLASS CONTAINING MANGANESE                                             GENERAL                                                                              GLASS CONTAINING                                                                           GLASS CONTAINING                              CONSTITUENTS                                                                              RANGE  BARIUM       IRON                                          __________________________________________________________________________    SiO.sub.2   59-65  59-65        60-64                                         Al.sub.2 O.sub.3                                                                          4-8    4-8          5-6.5                                         Na.sub.2 O  12.5-18                                                                              12.5-18      14.5-18                                       K.sub.2 O   0-3    0-3          0-3                                           R.sub.2 O = Na.sub.2 O + K.sub.2 O                                                        15-18  15-18        16-18                                         Al.sub.2 O.sub.3 /R.sub.2 O                                                               0.25/0.4                                                                             0.25-0.4     (0.25-0.4)                                    CaO         4.5-9  4.5-8        5-9                                           MgO         0-4    0-4          0-4                                           MgO/CaO     0/0.75 0/0.75       0/0.75                                        MgO + CaO   7-9.5  7-9.5        8-9.5                                         MnO         0-4    1-3.5        1.5-4                                         BaO         0-5    2-3.5        trace                                         Fe.sub.2 O.sub.3                                                                          0.1-5  0.1-1        0.8-3.5                                       MnO + BaO + Fe.sub.2 O.sub.3                                                              3.5-8  4-8          3.5-6.5                                       B.sub.2 O.sub.3                                                                           0-2    0-2          trace                                         Miscellaneous                                                                             ≦ 1                                                                           ≦ 1   ≦ 1                                    of which SO.sub.3                                                                         ≦ 0.6                                                                         ≦ 0.6 ≦ 0.6                                  __________________________________________________________________________

Within the ranges of Column A, it is preferred to use compositionsformulated to maintain equilibrium between the viscosity on one hand,and the devitrification temperature and the resistance to water on theother hand, which is particularly difficult to do with glass formulatedaccording to prior art techniques. Columns B and C of Table II giveranges for compositions containing manganese, and also formulated togive the equilibrium above referred to.

The glass of Column B may contain small amounts of boron to whichaddition of fairly small amounts of barium is contemplated.

Column C, in contrast, comprehends novel compositions such as thosenumbered 5, 6 and 7 of Table I. These are manganese and iron containingcompositions from which deliberate addition of barium and of boron isexcluded, although some traces may be present.

SPINNER ALLOY

With some of the hardest glasses, having viscosity of the order of 1000poises at temperatures above about 1150° C., and having adevitrification temperature of the order of 1030° C., it is hereincontemplated that the spinner be formed of an alloy of specialcomposition capable of withstanding the temperatures required.Furthermore, if this alloy is used with softer glasses, the lift of thespinner is increased. Such an alloy may be formulated as follows, theparts being indicated as percentages by weight:

                  TABLE III                                                       ______________________________________                                        Elements         Range                                                        ______________________________________                                        C                0.65-0.83                                                    Cr               27.5-31                                                      W                6-7.8                                                        Fe               7-10                                                         Si               0.7-1.2                                                      Mn               0.6-0.9                                                      Co               0-0.2                                                        P                0-0.03                                                       S                0-0.02                                                       Ni (Balance)     ˜59-50                                                 ______________________________________                                    

Alloys of this type are particularly desirable with spinners of largediameter, for instance of at least 400 mm diameter.

In addition to fiberization of so-called hard glasses, the use of thespinner alloy above referred to also provides for fiberization ofglasses of a broad range of compositions, including both hard and softglasses, with which latter (the soft glasses), the use of the spinneralloy increases the life of the spinner. Thus, the spinner formed withthe new alloy may be used with glasses having composition within theranges indicated in Table IV just below:

                  TABLE IV                                                        ______________________________________                                        SiO.sub.2         59-67                                                       Al.sub.2 O.sub.3  3-8                                                         Na.sub.2 O        12.5-18                                                     K.sub.2 O         0-3                                                         R.sub.2 O = Na.sub.2 O + K.sub.2 O                                                              15-18                                                       CaO               4.5-9                                                       MgO               0-4                                                         MgO/CaO           0-0.75                                                      MnO               0-4                                                         BaO               0-5                                                         Fe.sub.2 O.sub.3  0.1-5                                                       B.sub.2 O.sub.3   0-5                                                         Miscellaneous     ≦ 1                                                  of which SO.sub.3 ≦ 0.6                                                ______________________________________                                    

We claim:
 1. Fiberizable glass consisting essentially of the followingingredients in the amounts indicated by weight, and characterized by aviscosity in a range above 1000 poises at a temperature of about 950° C.up to about 5000 poises at a temperature of about 1050° C.:

    ______________________________________                                        SiO.sub.2        60- 64                                                       Al.sub.2 O.sub.3 5- 6.5                                                       Na.sub.2 O       14.5- 18                                                     K.sub.2 O        0- 3                                                         R.sub.2 O = Na.sub.2 O + K.sub.2 O                                                             16- 18                                                       Al.sub.2 O.sub.3 /R.sub.2 O                                                                    (0.25- 0.4)                                                  CaO              5- 9                                                         MgO              0- 4                                                         MgO/CaO          0/0.75                                                       MgO + CaO        8- 9.5                                                       MnO              1.5- 4                                                       BaO              trace                                                        Fe.sub.2 O.sub.3 0.8- 3.5                                                     MnO + BaO + Fe.sub.2 O.sub.3                                                                   3.5- 6.5                                                     Miscellaneous    ≦ 1                                                   of which SO.sub.3                                                                              ≦ 0.6                                                 ______________________________________                                    


2. Glass according to claim 1, characterized in that the proportions ofthe various constituents are, by weight, substantially (i.e., within upto about 5% plus or minus of the amount indicated for each ingredient),as follows:

    ______________________________________                                        SiO.sub.2        63.45                                                        Al.sub.2 O.sub.3 5.25                                                         Na.sub.2 O       14.95                                                        K.sub.2 O        2.25                                                         CaO              5.4                                                          MgO              4                                                            MnO              3                                                            Fe.sub.2 O.sub.3 0.84                                                         SO.sub.3         0.51                                                         ______________________________________                                    


3. Glass according to claim 1, characterized in that the proportions ofthe various constituents are, by weight, substantially (i.e., within upto about 5% plus or minus of the amount indicated for each ingredient),as follows:

    ______________________________________                                        SiO.sub.2          62.1                                                       Al.sub.2 O.sub.3   5.85                                                       Na.sub.2 O         14.55                                                      K.sub.2 O          2.7                                                        CaO                5.75                                                       MgO                2.75                                                       BaO                trace                                                      MnO                3.4                                                        Fe.sub.2 O.sub.3   1.88                                                       SO.sub.2           0.4                                                        TiO.sub.2          trace                                                      B.sub.2 O.sub.3    trace                                                      ______________________________________                                    


4. Glass according to claim 1, characterized in that the proportions ofthe various constituents are, by weight, substantially (i.e., within upto about 5% plus or minus of the amount indicated for each ingredient),as follows:

    ______________________________________                                        SiO.sub.2          60.3                                                       Al.sub.2 O.sub.3   6.35                                                       Na.sub.2 O         14.95                                                      K.sub.2 O          2.65                                                       CaO                6.25                                                       MgO                2.4                                                        MnO                2.9                                                        Fe.sub.2 O.sub.3   3.37                                                       SO.sub.3           0.36                                                       ______________________________________                                    


5. Glass fibers formed from fiberizable glass as defined in claim
 1. 6.Glass fibers formed from fiberizable glass as defined in claim
 2. 7.Glass fibers formed from fiberizable glass as defined in claim
 3. 8.Glass fibers formed from fiberizable glass as defined in claim
 4. 9.Glass fibers formed from glass consisting essentially of the followingingredients in the amounts indicated by weight:

    ______________________________________                                        SiO.sub.2          59-65                                                      Al.sub.2 O.sub.3   4-8                                                        Na.sub.2 O         12.5-18                                                    K.sub.2 O          0-3                                                        R.sub.2 O = Na.sub.2 O + K.sub.2 O                                                               15-18                                                      Al.sub.2 O.sub.3 /R.sub.2 O                                                                      0.25-0.4                                                   CaO                4.5-8                                                      MgO                0-4                                                        MgO/CaO            0/0.75                                                     MgO + CaO          7-0.75                                                     MnO                1-3.5                                                      BaO                2-3.5                                                      Fe.sub.2 O.sub.3   0.1-1                                                      MnO + BaO + Fe.sub.2 O.sub.e                                                                     4-8                                                        B.sub.2 O.sub.3    0-2                                                        Miscellaneous      ≦ 1                                                 of which SO.sub.3  ≦ 0.6                                               ______________________________________                                    